[PATCH 02/27] allow hard links to directories, opt-in for any filesystem

Patch seems to work, might want more testing.
It probably should not be applied without a discussion, especially
as no filesystem in kernel tree wants this. I am working on a fs that does.

---
--- include/linux/fs.orig.h 2006-02-27 21:45:26.000000000 -0800
+++ include/linux/fs.h 2006-02-27 21:48:17.000000000 -0800
@@ -83,6 +83,8 @@
/* public flags for file_system_type */
#define FS_REQUIRES_DEV 1
#define FS_BINARY_MOUNTDATA 2
+#define FS_ALLOW_HLINK_DIR 4 /* FS will accept hard links to directories */
+#define FS_ALLOW_USER_HLINK_DIR 8 /* And it makes sense for regular users */
#define FS_REVAL_DOT 16384 /* Check the paths ".", ".." for staleness */
#define FS_ODD_RENAME 32768 /* Temporary stuff; will go away as soon
* as nfs_rename() will be cleaned up
--- fs/namei.c.orig 2006-02-27 21:55:26.000000000 -0800
+++ fs/namei.c 2006-02-27 22:08:27.000000000 -0800
@@ -2107,7 +2107,14 @@
if (!dir->i_op || !dir->i_op->link)
return -EPERM;
if (S_ISDIR(old_dentry->d_inode->i_mode))
- return -EPERM;
+ {
+ if (!(old_dentry->d_sb->s_type->fs_flags & FS_ALLOW_HLINK_DIR))
+ return -EPERM;
+ if (!(old_dentry->d_sb->s_type->fs_flags
+ & FS_ALLOW_USER_HLINK_DIR)
+ && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ }

error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
-
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